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Mayo Clinic study shows that Green Tea slows the growth of a common leukemia

Jun 14, 2010

EGCG is the major antioxidant in Green Tea and in this new study from the Mayo Clinic in Rochester Minnesota an Extract of Green Tea high in EGCG fights cancer cells in patients with chronic lymphocytic leukemia (CLL). The EGCG-Green Tea concentrated extract reduced the number of cancer cells in patients during a phase II clinical trial.

“The benefits we have seen in most CLL patients who use the chemical suggest that it has modest clinical activity and may be useful for stabilizing this form of leukemia, potentially slowing it down,” Dr. Tait Shanafelt, a Mayo Clinic hematologist and lead author of the study, said in a statement citing that a larger Phase III clinical trial would be definitive. “These studies advance the notion that a nutraceutical like EGCG can and should be studied as cancer preventives,” Dr. Neil Kay, a hematology researcher whose laboratory first tested the green tea extract in leukemic blood cells from CLL patients, said in a statement. “Using nontoxic chemicals to push back cancer growth to delay the need for toxic therapies is a worthy goal in oncology research — particularly for forms of cancer initially managed by observation such as CLL.” Both doctors stress that EGCG is not a substitute for chemotherapy, and all patients in the study had CLL in its earliest stages and would normally not be treated until their disease worsened; however Green Tea-EGCG did inhibit worsening.

CLL is a blood cancer that is a cross between leukemia and lymphoma. Its progression is measured by the number of leukemia cells in the blood and bone marrow as well as the size of lymph nodes. In the Mayo study, the number of leukemia cells was reduced in one-third of patients, and the size of lymph nodes was reduced by at least 50 percent in 69 percent of patients. In addition, side effects were minimal.

The findings were presented at the annual meeting of the American Society of Clinical Oncology on June 7th, 2010.

  • In their previous Phase 1 study published in the May 2009 issue of the Journal of Clinical Oncology, researchers found that the leukemia cell count was reduced in one-third of the patients and that the majority of patients with enlarged lymph nodes due to CLL had a 50% or greater reduction in their lymph node size.

  • In the Phase 2 study the researchers used the highest dosage given in the Phase 1 study in treating an additional 36 CLL patients.

  • 69% of the patients in the Phase 2 study were helped

  • 31% of the patients had at least a 20% sustained reduction in their leukemia cell count

  • 69% of the patients with enlarged lymph nodes had a 50% or greater reduction in lymph node size.

The study was funded by grants from the National Cancer Institute, the Mayo Comprehensive Cancer Center, from donors and from patient advocacy foundations.


The following study was previously posted on our website on August 03, 2009; the above study shows that Green Tea treats early stage leukemia while the following